The present invention relates to a process for the production of vulcanizable plastic and rubber compositions filled with carbon black in which one or more organosilicon compounds are incorporated.
It has long been known that oxidic surfaces can be treated with organosilicon compounds containing alkoxy groups (U.S. Pat. No. 3,227,675; EP 0,177,674; EP-PS 0,126,871). The object of all these efforts was and is to establish a bond between the inorganic component, the oxidic filler, whether for example glass or even silicate fillers of the type used for example in the rubber industry (e.g., precipitated and pyrogenic silicas, clays, aluminum silicates etc.), and an organic polymer differing widely in its chemical composition. This generally leads to an improvement in the properties of the vulcanizates. Carbon blacks, for example furnace blacks, lampblacks and gas blacks are not included among the oxidic fillers. The reaction between the alkoxysilyl groups and the OH groups on the surface which takes place in oxidic filler substances cannot take place on the carbon black so that the establishment of a chemical bond between the carbon black and the organosilicon compound would not appear to be possible.
Although granular mixtures of carbon black and organosilicon compounds are known from DE-PS 2,747,277 (U.S. Pat. No. 4,128,438), these mixtures are used for more effectively incorporating the organosilicon compound in silica-containing rubber compounds. In this case, the carbon black merely acts as a carrier for liquid organic silanes which are to be converted into the solid state. The silane can be removed from such mixtures by extraction with organic solvents.
Since, hitherto, attempts have always been made to establish the properties of carbon-black-filled rubber vulcanizates through the use of carbon blacks differing in their structure and specific surface, the problem now arises of improving the properties of vulcanizates through the use of silane-modified carbon blacks.
According to German patent application P 40 23 537, it is possible by adopting a suitable procedure to bind considerable quantities of organosilicon compounds to carbon black, depending on the surface and structure of the carbon and also upon the type of compounds used.